How long have you run your carpc off battery?

Hi.
Just curious. How long have you guys run your carpc's off the battery alone with the engine off? Were you using a DC-DC PSU, or a inverter? Approximately how much power were you drawing and how big is your battery?

I have a 52 amp hour stock battery and I am paranoid about my carpc draining it. I think I might get a second deep cycle battery which my carpc will run off, and I will use a relay to completely isolate that second battery from the main electrical system when the car is off. This way, I wont have to worry about my carpc draining my main battery and preventing me from starting my car (eg. if my computer hangs on shutdown).

So far I would say like 40 minutes while copying a dvd b4 taking it back to block buster. Using a carnetix 1900. But one time I put the carpc in hibernate and left it for 15 minutes and the car acted funny starting up. But i need to get at tune up and a new battery.

Car PC Status {------- }0%

Car Died along with Autonode Monitor after returned to me. Worked for 3 Months then died again. The car engined died not long after!